Spark-plug



W. M. SUBLETTE.

SPARK'FLUG. APPLICATION 'FILED JAN. 13, |919.

Patented Oct. 5, 1920.

INVENTOR. WIW/'am /l/. Subleie BY om@ fen/m74@ ATTORNEYS.

marrer)A STATI-:s

PATENT kFFIC *WILLIAM M. SUBLETTE, or Los ANGELES, CALIFORNIA, AssIGNoa or oN-n-IIALI1 'ro cIIAUNcEY 1v1. BLAIR, or Los ANGELES, CALIFORNIA.

sPAnK-PLUG.

Specification of Letters Patent.

Patented. oet. 5, 1920.

Application led January 13, 1919. Serial No. 270,329.

y following is a specification.

This invention relates to spark plugs for internal combustion engines, and the main object of the invention is to provide a spark plug which will be substantially protected from breakage or other damage by rough handling or by accidental impact of tools or Aother objects therewith. I

The accompanying drawings illustrate an embodiment of my invention, and referring thereto: y

Figure 1 is a vertical section of the plug.

Fig. 2 is a plan viewY artly in horizontal section on line 2 2 in4 ig. 1.

Fig. 3 is a fragmentary section of the upper part of the plug, showing the connecting device separate therefrom.

' Thespark plug comprises an outer body -1, of metal, and insulator body 2, mounted within said outer body andsupporting the point 3 for the spark gap, and a casing 4 inclosing said insulator body 2 to rotect and .retain the same` in position, and Yormed as-a metal sleeve. f

The outer body 1 is provided with screw means 5 for screwing into the cylinder wall to hold the spark plug in position, and with wrench hold 6 to enable it to be turned bya suitable tool. At its-inner end the body 1 is formed with a cylindrical chamber 8 having -an internal flange 9 which forms the grounded member for the spark gap, the point 3 extending within the opening 9 formed by said ange. Outwardly from the'chamber 8, the body 1 is formed with a tubular portion 10 of larger diameter than chamber 8, so as to form a shoulder 11, and this enlarged portion of the body 1 is 4screwthreaded at 12 to receive and engage the screw thread 13 on casing or sleeve 4.-

Insulator body 2 is preferably of porcelain or similar material, and is provided with an annular ange 14, which is clamped between' shoulder 11, and the inner end of sleeve 4, suitable packing and cushioning means such as insulating washers 13 and 13 (of asbestos renforced with copper in well known manner, or of other suitable material) being interposed between 4said anges and the abutting parts. Insulator body 2 has a portion extending outwardly from flange 14 and surrounded by casing 4, and a portion extending inwardly from said flan e. Y The outer end of insulator body 2 is pre erably tapered or inclined so as to shed water, and the sleeve or casing 4, which surrounds and preferably extends somewhat beyond the outer end of the insulator may rbe channeled at 18 to draw off any water that may leak on to the plug. An insulating sleeve or tube 15 of mica or other comparatively non-frangible insulating material, is interposed between sleeve or casing 4 and insulator body 2.

lnsulator body 2 is provided with a recess 20 at its upper' end, with a cylindrical chamber 21 at its inner end with a contracted opening 22 between recess 2O and chamber 21, forming a shoulder 20 at the inner end of recess 20. A metal screw 23 engages by its head 23 with the shoulder 20 and extends axially through opening 22 and chamber 21 and carries the spark plug point 3 at its lower end, a nut 25 on said screw engaging the lowen end of insulator body 2 to retain'the screw in position. A helical spring .26 has one end secured under the head 23 and a metal screw 30 extending axially in said holly and fastened thereto by nut 31 and head 32. Said connecting device is placed in position by inserting it within the helical spring 26, turning it at the same time so as to tend to expand the spring laterally, and the spring then gripping the device and making metallic connection between thesame and the screw 23, while giving suiiiciently resilient support to the connecting device to prevent undue' strain on the insulator vbody 2 when said device is accidentally displaced laterally.

The outer'casing or sleeve 4 being of metal protects the relatively frangible insulator body 2, but even if the latter be cracked, it will still be retained in position by inclosing parts 1 and 4, and the insulation would still be effective on account of the relatively nonfrangible insulating sleeve 15 and washers and preferably overlapping so as to insure protection of the insulation.

The connecting device sleeve or body 29 may have an enlargement 34 extending over the insulator body to assist in shedding i water therefrom.

WhatV I claim is:

1. A spark plug comprising a metal body having a shoulder, a casing screwing into said body7 a porcelain insulator body having a flange secured between said shoulder and the inner end of said casing and havin portions extending respectively outwa and inward from said-Harige, a sleeve of relatively non-frangible insulating material surrounding said outward extension of said porcelain insulator body and surrounded by said casing, a metallic member extendinof axially in said porcelain insulator body and formed at its inner end to coperate with a part of the first named metal body to pro vide a spark gap, and a sleeve of relatively non-frangible `material within said inwardlyv extending portion of said porcelain body and surrounding said metallic member.

2. A construction as set forth in claim 1, in which the said sleeves of relatively nonfrangible material overlap each other for the purpose set forth. l

3. rhe combination with a spark plug insulator member having a recess,A a metal member mounted in said recess and extending through said insulator and carrying .a spark point at its inner end', and a connecting device seated in said recess and having an insulating body portion, provided with an enlargement projecting over the first named insulator body and with a metal portion having a detachable connection 'with the first named metal memberand extending to the outside of the recess for connection to an electrical circuit. "e

In testimony whereof I have hereunto subscribed my name this 3d day of January 1919.

WILLAM M. SUBLETTE. 

